Lung Carcinoid Tumor

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Causes, Risk Factors, and Prevention TOPICS

Do we know what causes lung carcinoid tumors?

Not much is known about what causes lung carcinoid tumors. Researchers have learned a lot about how certain risk factors like cancer-causing chemicals or radiation can cause changes in lung cells that lead to carcinomas, the more common type of lung cancer. But these factors are not thought to play a large role in the development of lung carcinoid tumors.

Carcinoid tumors probably develop from tiny clusters of neuroendocrine cells in the lung airways called carcinoid tumorlets. Tumorlets are sometimes found unexpectedly in lung biopsies done to treat or diagnose other conditions. Under the microscope, tumorlets resemble carcinoid tumors, except that they are much smaller – less than 5 mm (about ¼ inch) across. Most tumorlets never grow any bigger, but some may eventually become carcinoid tumors.

Researchers have found some chromosome and gene changes that are common in lung carcinoid tumor cells. Chromosomes are long strands of DNA in each of our cells that contain our genes – the instructions for how our cells function. But it is still not clear exactly how these changes cause carcinoid tumorlets to develop from lung neuroendocrine cells or how they might cause tumorlets to grow to become carcinoid tumors.

Last Medical Review: 11/13/2013
Last Revised: 11/13/2013